[PATCH v2 5/5] cpuidle: psci: Prevent domain idlestates until consumers are ready

[Lukasz Luba]

On 7/7/20 1:58 PM, Ulf Hansson wrote:
> Depending on the SoC/platform, additional devices may be part of the PSCI
> PM domain topology. This is the case with 'qcom,rpmh-rsc' device, for
> example, even if this is not yet visible in the corresponding DTS-files.

I was interested by your description and checked related DT
to this device. It's probably the best what we can do in such situation
and such requirements.

> 
> Without going into too much details, a device like the 'qcom,rpmh-rsc' may
> have HW constraints that needs to be obeyed to, before a domain idlestate
> can be picked.
> 
> Therefore, let's implement the ->sync_state() callback to receive a
> notification when all consumers of the PSCI PM domain providers have been
> attached/probed to it. In this way, we can make sure all constraints from
> all relevant devices, are taken into account before allowing a domain
> idlestate to be picked.
> 
> Acked-by: Saravana Kannan <saravanak at google.com>
> Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>



Reviewed-by: Lukasz Luba <lukasz.luba at arm.com>

> ---
>   drivers/cpuidle/cpuidle-psci-domain.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/cpuidle/cpuidle-psci-domain.c b/drivers/cpuidle/cpuidle-psci-domain.c
> index bf527d2bb4b6..b6e9649ab0da 100644
> --- a/drivers/cpuidle/cpuidle-psci-domain.c
> +++ b/drivers/cpuidle/cpuidle-psci-domain.c
> @@ -27,6 +27,7 @@ struct psci_pd_provider {
>   };
>   
>   static LIST_HEAD(psci_pd_providers);
> +static bool psci_pd_allow_domain_state;
>   
>   static int psci_pd_power_off(struct generic_pm_domain *pd)
>   {
> @@ -36,6 +37,9 @@ static int psci_pd_power_off(struct generic_pm_domain *pd)
>   	if (!state->data)
>   		return 0;
>   
> +	if (!psci_pd_allow_domain_state)
> +		return -EBUSY;
> +
>   	/* OSI mode is enabled, set the corresponding domain state. */
>   	pd_state = state->data;
>   	psci_set_domain_state(*pd_state);
> @@ -222,6 +226,15 @@ static void psci_pd_remove_topology(struct device_node *np)
>   	psci_pd_init_topology(np, false);
>   }
>   
> +static void psci_cpuidle_domain_sync_state(struct device *dev)
> +{
> +	/*
> +	 * All devices have now been attached/probed to the PM domain topology,
> +	 * hence it's fine to allow domain states to be picked.
> +	 */
> +	psci_pd_allow_domain_state = true;
> +}
> +
>   static const struct of_device_id psci_of_match[] = {
>   	{ .compatible = "arm,psci-1.0" },
>   	{}
> @@ -289,6 +302,7 @@ static struct platform_driver psci_cpuidle_domain_driver = {
>   	.driver = {
>   		.name = "psci-cpuidle-domain",
>   		.of_match_table = psci_of_match,
> +		.sync_state = psci_cpuidle_domain_sync_state,
>   	},
>   };
>   
>